This invention relates to control means for a drier or for use in a developer, printer, or the like having a drier.
In a conventional drier, automatic film developer, or printer, a photosensitive film which is developed and washed by water is dried in a short time by warm air in a drying tank.
In such a conventional automatic developer, the primary use of electricity is the drier. In order to save power, the supply of electric power to the drier should be stopped when no film is fed to the developer. Electric power should be automatically supplied to the drier when film is inserted in the developer. By the time the film reaches the drying tank after passing through the developing tank and the washing tank, the warm air necessary for drying is available in the drying tank.
However, since the drier has a large heat capacity, a relatively long time is needed to raise the temperature of the air to the proper degree. The first photosensitive film in a series to enter the drier often cannot be dried completely when the drier starts heating from room temperature.
On the other hand, when a heater is used that is sufficiently large to dry the first film completely, excessive electric power is consumed for drying the following films, which is uneconomical.
In order to solve this problem, the drier is preheated and the blower that moves the air during drying is stopped to prevent the drier from cooling completely when no film is being fed or the developing operation is stopped. This can be performed in several ways. For example, the heater may be operated at a low voltage, or the rated electric power may be intermittently supplied to the heater. However, in the former embodiment, a large-sized transformer is required, which means high cost. In the latter embodiment, the nichrome wires of the heater are overheated because the blower is stopped during the stop of the developing operation, resulting in deformation of the nichrome wires.